There is no question that a lack of fans leads to greater runs.
The refs don't "feel" it... and as much as they swear they "tune out the crowd and are unaffected...", I can show you at least 2,000 extremely exaggerated "charge calls" after 2 or 3 straight buckets in a home team comeback that would demonstrate otherwise.
Crowds also tend to quell visiting runs.... but even more so, they keep foul levels closer to "even" for the home team. If it's 10 fouls on the home team and 3 on the visitors, there will be NO WAY the officials aren't reminded and feeling that. And human nature is called nature for a reason. This year, more than ever, you're seeing inequitable foul figures in favor of ROAD teams at times. Such a weird thing to see.
That has been the single biggest difference in basketball this year. Road wins are just "easier", in ways that ar far more significant than just crowd sound/vibe.